There are many ways that Oda could write Imu's Defeat here, not permanently but at least weaken him so that next Arc He won't Fight & only become a living source of power,
However, I'm gonna pretend that Oda won't go the obvious way & Imu will actually win, but without SHs Efforts being useless, so which Scenario helps fulfill Imu's Goal? But at same time Elbaph Kids do not leave & SHs aren't taken out?
There is one scenario that I always keep thinking about, and it's instead of Imu going back to Mary Geoise or taking Kids there, He will bring Mary Geoise to Elbaph, basically imagine Imu is losing, we see that "Defeat" Scene similar to how Saturn was defeated by Bonney & Luffy in a symbolic way rather than actually knocked out, but after that He starts to prepare something massive, basically like when Pain prepared to nuke Konoha, and they realize something bad is gonna happen, and they try to stop it but fail,
Imu uses all his energy to open a massive portal & teleport entire Mary Geoise on top of Elbaph in Heaven World, declaring "Ragnarok" & that marks beginning of Enies Lobby-Like 2nd Part of this Saga, and I think this is the event that Oda hyped up recently in some jump message (Forgot which one),
Now imagine such News? How wd everyone react hearing that Mary Geoise is no longer on Red Line & it's actually in Elbaph now?
Red-Hair Pirates, Cross Guild, Blackbeard Pirates, Marine HQ, Cipher-Pol 0, Gorosei/Holy Knights, Revos Army, Sword, Neo Mads & many other Factions will all head towards Elbaph,
Endgame Battle Royale, where Oda will get rid of 99.99% of Main Cast.